340 M. Weltnev on the Survival o/" Spongillee 



The following table will serve to show how Sc. valida^ 

 Lucas^ may be distinguished from the allied South-American 

 species, which agree with it in possessing spines upon the 

 femora of the nineteenth and twentieth pairs of legs and a 

 deep transverse furrow upon the first dorsal plate : — 



A. Sternites smooth, not bisulcated; patellae of 



anal legs armed with spines prasina, C. Kocb, 



S. Amer. 



B. Sternites bisulcated. 



a. Last tergite with a median longitudinal 



crest viridicornis, Newp. 



S. Amer. 



b. Last tergite without a median longitudinal 



crest. 



a. Femora of all the legs armed ; patella 



of anal leg armed giy^^s. Leach. S. 



Amer. 



b. Femora of nineteenth and twentieth 



pairs of legs armed ; patella of anal 



leg unarmed valida, Lucas. N. 



Afr. 



XLI. — On the Survival of Spongillse after the Development 

 of Swarm-larvas. By M. Weltner*. 



The assertion made by Laurent (1844) that our freshwater 

 sponges perish after the development of swarm-larvge was 

 disputed by Lieberkiihn (1857). Marshall (1884) supposes 

 that there is an alternation of generations in Spongilla lacus- 

 tris. From the gemmulai which live through the winter 

 there originate in the spring male and female Spo^igillce which 

 fertilize one another. The males die after the development of 

 the semen ; the females, after the coming forth of the larvse, 

 become neuters and perish in the autumn with formation of 

 gemmules. The oftspring of the male and female specimens 

 remain neuters in the first year and likewise break up into 

 gemmules in the autumn. 



Gotte (1886), on the contrary, is of opinion that reproduc- 

 tion universally causes the death not only of the Spongilloe^ 

 but of sponges in general. The parts aft'ected by the repro- 



* Translated from a separate copy of the paper in the 'Sitzungs- 

 berichte der Gesellschaft naturforschender Freuude zu Berlin/ February 

 21, 1888, pp. 18-22, communicated by H. J. Carter, F.R.S. 



